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powerpc/32: Don't always pass -mcpu=powerpc to the compiler

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Since commit 4bf4f42a2f ("powerpc/kbuild: Set default generic
machine type for 32-bit compile"), when building a 32 bits kernel
with a bi-arch version of GCC, or when building a book3s/32 kernel,
the option -mcpu=powerpc is passed to GCC at all time, relying on it
being eventually overriden by a subsequent -mcpu=xxxx.

But when building the same kernel with a 32 bits only version of GCC,
that is not done, relying on gcc being built with the expected default
CPU.

This logic has two problems. First, it is a bit fragile to rely on
whether the GCC version is bi-arch or not, because today we can have
bi-arch versions of GCC configured with a 32 bits default. Second,
there are some versions of GCC which don't support -mcpu=powerpc,
for instance for e500 SPE-only versions.

So, stop relying on this approximative logic and allow the user to
decide whether he/she wants to use the toolchain's default CPU or if
he/she wants to set one, and allow only possible CPUs based on the
selected target.

Reported-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/d4df724691351531bf46d685d654689e5dfa0d74.1657549153.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2022-07-11 16:19:30 +02:00 committed by Michael Ellerman
parent 9be013b2a9
commit 446cda1b21
2 changed files with 19 additions and 28 deletions
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26
arch/powerpc/Makefile
View File

@ -15,23 +15,6 @@ HAS_BIARCH := $(call cc-option-yn, -m32)
# Set default 32 bits cross compilers for vdso and boot wrapper
CROSS32_COMPILE ?=
ifeq ($(HAS_BIARCH),y)
ifeq ($(CROSS32_COMPILE),)
ifdef CONFIG_PPC32
# These options will be overridden by any -mcpu option that the CPU
# or platform code sets later on the command line, but they are needed
# to set a sane 32-bit cpu target for the 64-bit cross compiler which
# may default to the wrong ISA.
KBUILD_CFLAGS += -mcpu=powerpc
KBUILD_AFLAGS += -mcpu=powerpc
endif
endif
endif
ifdef CONFIG_PPC_BOOK3S_32
KBUILD_CFLAGS += -mcpu=powerpc
endif
# If we're on a ppc/ppc64/ppc64le machine use that defconfig, otherwise just use
# ppc64_defconfig because we have nothing better to go on.
uname := $(shell uname -m)
@ -183,6 +166,7 @@ endif
endif
CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
# Altivec option not allowed with e500mc64 in GCC.
ifdef CONFIG_ALTIVEC
@ -193,14 +177,6 @@ endif
CFLAGS-$(CONFIG_E5500_CPU) += $(E5500_CPU)
CFLAGS-$(CONFIG_E6500_CPU) += $(call cc-option,-mcpu=e6500,$(E5500_CPU))
ifdef CONFIG_PPC32
ifdef CONFIG_PPC_E500MC
CFLAGS-y += $(call cc-option,-mcpu=e500mc,-mcpu=powerpc)
else
CFLAGS-$(CONFIG_E500) += $(call cc-option,-mcpu=8540 -msoft-float,-mcpu=powerpc)
endif
endif
asinstr := $(call as-instr,lis 9$(comma)foo@high,-DHAVE_AS_ATHIGH=1)
KBUILD_CPPFLAGS += -I $(srctree)/arch/$(ARCH) $(asinstr)

21
arch/powerpc/platforms/Kconfig.cputype
View File

@ -135,9 +135,9 @@ config GENERIC_CPU
select ARCH_HAS_FAST_MULTIPLIER
select PPC_64S_HASH_MMU
config GENERIC_CPU
config POWERPC_CPU
bool "Generic 32 bits powerpc"
depends on PPC32 && !PPC_8xx
depends on PPC32 && !PPC_8xx && !PPC_85xx
config CELL_CPU
bool "Cell Broadband Engine"
@ -196,11 +196,23 @@ config G4_CPU
depends on PPC_BOOK3S_32
select ALTIVEC
config E500_CPU
bool "e500 (8540)"
depends on PPC_85xx && !PPC_E500MC
config E500MC_CPU
bool "e500mc"
depends on PPC_85xx && PPC_E500MC
config TOOLCHAIN_DEFAULT_CPU
bool "Rely on the toolchain's implicit default CPU"
depends on PPC32
endchoice
config TARGET_CPU_BOOL
bool
default !GENERIC_CPU
default !GENERIC_CPU && !TOOLCHAIN_DEFAULT_CPU
config TARGET_CPU
string
@ -215,6 +227,9 @@ config TARGET_CPU
default "e300c2" if E300C2_CPU
default "e300c3" if E300C3_CPU
default "G4" if G4_CPU
default "8540" if E500_CPU
default "e500mc" if E500MC_CPU
default "powerpc" if POWERPC_CPU
config PPC_BOOK3S
def_bool y